The main function of the lung is to exchange gasses between the ambient air and the blood. Within this framework O2 is transferred from the environment to the blood while CO2 is eliminated from the body.
In a normal resting human these processes are associated with an O2 input of about 200-250 cm3/min and an output of about the same amount of CO2. This exchange is made through a surface area of 50-100 m2 of a 0.5-1 μm thick biological membrane separating the alveolar air from the pulmonary blood. This process is associated with the flow of similar volumes of blood and air—about 5 Liter/min. At the given flow rate the blood is in “contact” with the membrane through which diffusion takes place for a time period of ⅓-⅕ sec.
In natural systems such as the lung the gas exchange is achieved by diffusion taking place across a thin biological membrane separating two compartments: the gases in the lung alveoli and the gases contained in the blood of the lung capillaries. The gases in the alveolar compartment are maintained at a composition close to that of ambient air or gas by moving the air or gases in and out of the lungs by respiratory movements. The gas exchange is achieved by diffusion through the surface area of the exchange membrane that is extremely large—about 70 m2. The driving force for diffusion of gases into and out of the blood is maintained by a very large blood flow through the lung capillaries.
Nanotubes (“NT”) are inert cylindrical structures having diameters of about 1-100 nm. In the case of carbon NT they are constructed of one or more layers of hexagonal carbon atom mesh. Their length can reach values in the cm range. FIG. 1A depicts a single wall NT made of carbon. At this time, NTs are well-known structures, and ways to make NTs are also well known. FIG. 1B depicts a scanning electron microscope photo of a matrix of parallel aligned carbon nanotubes.
Nanofibers are similar structures made out of carbon, silicon, etc. and are also commercially available. Nanofibers are defined as fibers with diameters less than 100 nanometers (see ref 1). In the textile industry, this definition is often extended to include fibers as large as 1000 nm diameter (see ref 2). Carbon nanofibers are graphitized fibers produced by catalytic synthesis. Inorganic nanofibers (sometimes called ceramic nanofibers) can be prepared from various kinds of inorganic substances, the most frequently mentioned ceramic materials with nanofiber morphology are titanium dioxide (TiO2), silicon dioxide (SiO2), zirconium dioxide (ZrO2), aluminum oxide (Al2O3), lithium titanate (Li4Ti5O12), titanium nitride (TiN) or platinum (Pt).